Reflective mask blank and method for producing the same

Abstract

SOLUTION: To provide a reflection type mask blank that selects a metal element or a metalloid element constituting an absorber film of the reflection type mask blank from a first element included in a first region, a second element included in a second element and a third element included in a third region, which are determined by a refractive index n and an extinction coefficient k of the metal element or the metalloid alone, and forms the absorber film as a film having a reflectance ratio of 0.05-0.25 and a function of shifting a phase with a phase difference of 180-260 degrees.EFFECT: A reflection type mask blank has an absorber film which secures a reflectance ratio and phase difference required for a reflection type mask using a phase shift function of enhancing a contrast of an optical image (projection image) of a pattern and has a thinner film thickness. A reflection type mask blank having an absorber film requiring various reflectance ratios and phase differences as such the reflection type mask blank can be effectively manufactured.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a reflective mask blank used in the manufacture of a reflective mask used in the manufacture of semiconductor devices and the like, in particular a reflective mask blank capable of providing high pattern transfer performance when made into a reflective mask, and a method for manufacturing the same. [Background technology]

[0002] In the manufacturing process of semiconductor devices (semiconductor device), photolithography technology is repeatedly used, in which exposure light is irradiated onto a transfer mask, and the circuit pattern formed on the mask is transferred onto a semiconductor substrate (semiconductor wafer) via a reduced projection optical system. Conventionally, the wavelength of the exposure light has been mainly 193 nm using argon fluoride (ArF) excimer laser light, and a process called multi-patterning, which combines exposure processes and processing processes multiple times, has been used to ultimately form patterns with dimensions smaller than the exposure wavelength.

[0003] However, as the continuous miniaturization of device patterns requires the formation of even finer patterns, EUV lithography technology using extreme ultraviolet (EUV) light with a shorter wavelength than ArF excimer laser light as exposure light has been proposed. EUV light is light with a wavelength of about 0.2 to 100 nm, more specifically, light with a wavelength of about 13.5 nm. Since this EUV light has extremely low permeability to materials, a reflective exposure optical system and a reflective mask different from the conventional one are used. A reflective mask is a mask in which a multilayer reflective film that reflects EUV light and its protective film are formed on a substrate, and an absorber film that absorbs EUV light is formed in a pattern on top of the multilayer reflective film. Here, the state before the absorber film is patterned (including the state where a resist layer is formed) is called a reflective mask blank, and this is used as a material for a reflective mask (hereinafter, a reflective mask blank that reflects EUV light is also called an EUV mask blank).

[0004] In a typical reflective mask that reflects EUV light, the EUV light incident on the reflective mask mounted on the exposure tool (pattern transfer tool) is reflected at a certain reflectance in the area without the absorber film, but is absorbed in the area with the absorber film, reducing the reflectance and hardly reflecting it at all. This allows the optical image of the pattern formed on the reflective mask to be transferred as a projected image onto the semiconductor substrate. At present, when an absorber film mainly composed of Ta (tantalum) is used, the reflectance is about 1% at a film thickness of 70 nm. On the other hand, since the reflectance of the multilayer reflective film is effectively 65 to 67%, the ratio (reflectance ratio) of the reflectance of the absorber film (absorber pattern) to the reflectance of the area without the absorber film (area where the multilayer reflective film and its protective film are exposed) in the reflective mask is about 1.5 to 2%.

[0005] On the other hand, by setting the phase difference (phase shift) between the light slightly reflected from the part with the absorber film and the light reflected from the part without the absorber film to generate a phase difference of, for example, 180 degrees, and using this phase difference, it is possible to obtain a high contrast in the optical image of the pattern formed on the reflective mask. In particular, in a fine dimensional area, a reflectance ratio of 1.5 to 2% is insufficient in the contrast of the projected image of the pattern transferred onto the semiconductor substrate, so that the use of the phase difference is essential. Technologies related to reflective mask blanks for manufacturing EUV masks taking such phase difference into consideration are disclosed, for example, in JP 2006-228766 A (Patent Document 1) and JP 2011-29334 A (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-228766 A [Patent Document 2] JP 2011-29334 A Summary of the Invention [Problem to be solved by the invention]

[0007] The reflectance ratio (1.5-2%) of an absorber film mainly composed of Ta (tantalum) is one order of magnitude larger than the light shielding ratio of a light shielding film in a transmission type photomask using ArF excimer laser light, but even if the absorption performance is somewhat low, there is an advantage in that the contrast of the optical image (projected image) of the pattern can be obtained by the phase shift action if there is a phase difference. On the other hand, in finer dimensional areas, the three-dimensional effect due to the thickness of the absorber film, the so-called shadowing effect, appears significantly, so in order to reduce this, the absorber film must be made thin. However, when the absorber film is made thin, the phase difference also decreases with the increase in the reflectance ratio, and the phase shift action becomes smaller, resulting in a problem that the contrast of the optical image (projected image) of the pattern cannot be obtained sufficiently.

[0008] Furthermore, the reflectance ratio and phase difference required in a reflective mask using a phase shift function vary depending on the shape and density of the pattern to be transferred, the illumination conditions for the pattern, etc. These parameters can be obtained by optical simulation, and the values ​​of optical constants required for the absorber film, such as the refractive index n and the extinction coefficient k, can be obtained by setting the thickness of the absorber film. However, with a single type of metal or semimetal material, there is practically no material that can satisfy the values ​​of the optical constants required for the absorber film, and it is difficult to achieve this with a single type of metal or semimetal material. In addition, neither JP 2006-228766 A (Patent Document 1) nor JP 2011-29334 A (Patent Document 2) takes into consideration setting the reflectance ratio and phase difference required in a reflective mask depending on the shape and density of the pattern to be transferred, the illumination conditions for the pattern, etc.

[0009] The present invention has been made to solve the above-mentioned problems, and has an object to provide a reflective mask blank having a thinner absorber film that ensures the necessary reflectance ratio and phase difference in a reflective mask utilizing a phase shift function, and a method for effectively manufacturing such a reflective mask blank utilizing a phase shift function. [Means for solving the problem]

[0010] The present inventors conducted extensive research to solve the above problems, and as a result, found that a reflective mask blank having a thinner absorber film that ensures the necessary reflectance ratio and phase difference in a reflective mask utilizing a phase shift function can be effectively formed by forming the absorber film from a material containing, as metal elements or semi-metal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group specified by a refractive index n and an extinction coefficient k, where one or more elements are selected from each of the two or three element groups.

[0011] The present inventors have found that by forming the absorber film of such a reflective mask blank by selecting one or more elements from each of two or three regions selected from a first region, a second region, and a third region specified by a refractive index n and an extinction coefficient k as a metal element or a semi-metal element, and setting the contents of these elements so that the reflectance ratio and phase difference of the absorber film become predetermined reflectance ratios and phase differences, it is possible to efficiently select a material effective for an absorber film that gives a reflectance ratio and phase difference required in a reflective mask according to the shape and density of a pattern to be transferred, illumination conditions for the pattern, and the like, based on optical constants such as the refractive index n and the extinction coefficient k, and to form an absorber film with a thinner film thickness that ensures the required reflectance ratio and phase difference using the selected material, thereby completing the present invention.

[0012] Accordingly, the present invention provides the following reflective mask blank and method for producing the same. 1. A reflective mask blank comprising a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of the incident EUV light and reflects the remainder, formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film to EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25, The absorber film changes the phase of the reflected light relative to the phase of the reflected light from the multilayer reflective film and the protective film. 200 It has a phase shift function of up to 260 degrees. the absorber film is made of a material containing, as metal elements or semimetal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group, and at least one element selected from each of the two or three element groups; When the refractive index of each of the metal or metalloid elements included in each of the first element group, the second element group, and the third element group is n and the extinction coefficient of each of the metal or metalloid elements included in each of the first element group, the second element group, and the third element group is k, The metal or metalloid element contained in the first element group is represented by the following formula (1): k≦0.01 (1) is an element that satisfies the following: The metal or metalloid element included in the second element group is a metal or metalloid element not included in the first element group, and is represented by the following formula (2): n+2k≧0.99 (2) is an element that satisfies the following: The metal or metalloid element included in the third element group is a metal or metalloid element not included in the first element group or the second element group, and is represented by the following formula (3): n≦0.89 (3) It is an element that satisfies A reflective mask blank comprising: 2. The metal or metalloid elements in the first element group are Mo, Nb, Zr, Si, and Y; the metal or metalloid elements in the second element group are W, Au, Ir, V, Pt, Cr, Ta, Hf, Co, Ni, Sn, and Te; The metal or metalloid elements included in the third element group are Ru, Rh, and Pd. 2. The reflective mask blank according to claim 1. 3 The absorber film is characterized in that the content of each of the three or more elements selected from the group of elements is 5 atomic % or more. or 2 The reflective mask blank according to claim 1. 4The absorber film changes the phase of the reflected light relative to the phase of the reflected light from the multilayer reflective film and the protective film. 200 1 to 3, characterized in that the phase difference between the input and output signals is 1 to 240 degrees. 3 13. The reflective mask blank according to any one of claims 1 to 12. 5 A reflective mask blank having a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of the incident EUV light and reflects the remainder, formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film to EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25, the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, The absorber film is made of a material containing, as metal elements or semimetal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group, and at least one element selected from each of the two or three element groups. 、 before The metal or metalloid element included in the first element group is Mo, Nb, Zr, Si and Y and The metal or metalloid element included in the second element group is W, Au, Ir, V, Pt, Cr, Hf, Co, Sn and Te and The metal or metalloid element included in the third element group is Ru, Rh and Pd is A reflective mask blank comprising: 6 The absorber film is characterized in that the content of each of the three or more elements selected from the group of elements is 5 atomic % or more. 5 The reflective mask blank according to claim 1. 7A reflective mask blank having a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of the incident EUV light and reflects the remainder, formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film to EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25, the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, the absorber film is made of a material containing, as metal elements or semimetal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group, and at least one element selected from each of the two or three element groups; When the refractive index of each of the metal or metalloid elements included in each of the first element group, the second element group, and the third element group is n and the extinction coefficient of each of the metal or metalloid elements included in each of the first element group, the second element group, and the third element group is k, The metal or metalloid element contained in the first element group is represented by the following formula (1): k≦0.01 (1) is an element that satisfies the following: The metal or metalloid element included in the second element group is a metal or metalloid element not included in the first element group, and is represented by the following formula (2): n+2k≧0.99 (2) is an element that satisfies the following: The metal or metalloid element included in the third element group is a metal or metalloid element not included in the first element group or the second element group, and is represented by the following formula (3): n≦0.89 (3) It is an element that satisfies the following criteria: the law of nature, The content of each of the three or more elements selected from the group of elements in the absorber film is 5 atomic % or more. R A reflective mask blank comprising: 8 The metal or semimetal elements included in the first element group are Mo, Nb, Zr, Si, and Y; the metal or metalloid elements in the second element group are W, Au, Ir, V, Pt, Cr, Ta, Hf, Co, Ni, Sn, and Te; The metal or metalloid elements included in the third element group are Ru, Rh, and Pd. Characterized by 7 The reflective mask blank according to claim 1. 9 The absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 240 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film. 5 ~ 8 13. The reflective mask blank according to any one of claims 1 to 12. 10 The metal or metalloid element included in the first element group is Mo, the metal or metalloid element included in the second element group is W; The metal or metalloid element included in the third element group is Ru. 1. or 9 The reflective mask blank according to claim 1. 11 A conductive film is formed on the other main surface of the substrate. 10 13. The reflective mask blank according to any one of claims 1 to 12. 12. A reflective mask blank according to any one of 1 to 11, wherein the absorber film has a thickness of 30 nm or more and 65 nm or less. 13 A reflective mask blank having a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of the incident EUV light and reflects the remainder formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film to EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25, the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, A method for producing a reflective mask blank, wherein the absorber film contains a metal element or a metalloid element, When the refractive index of the metal element or metalloid element alone is n and the extinction coefficient of the metal element or metalloid element alone is k, The refractive index n and the extinction coefficient k are expressed by the following formula (1): k≦0.01 (1) A first element included in a first region in the range indicated by The refractive index n and the extinction coefficient k are of The range is not included in the region, and is expressed by the following formula (2). n+2k≧0.99 (2) A second element included in a second region in the range indicated by A range not included in the first region or the second region, and a range represented by the following formula (3) n≦0.89 (3) A third element in a third region in the range indicated by A step of classifying selecting, from two or three regions selected from the first region, the second region, and the third region, three or more elements, the one or more elements being selected from each of the two or three regions; The absorber film has a thickness that satisfies the ratio (R A / R B determining the content of each of the three or more elements selected from the region so as to obtain a predetermined ratio within the range of (a) and a predetermined phase difference within the range of the phase difference; and forming an absorber film from a material containing each of the three or more elements selected from the region at the determined content ratio; A method for producing a reflective mask blank, comprising: 14 The method includes forming a conductive film on the other main surface of the substrate. 13 The manufacturing method described in 15 The absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 240 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film. 13 or14 The manufacturing method described in The present invention also relates to the following reflective mask blank. [1] A reflective mask blank having a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of the incident EUV light and reflects the remainder formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film to EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25, the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, the absorber film is made of a material containing, as metal elements or semimetal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group, and at least one element selected from each of the two or three element groups; When the refractive index of each of the metal or metalloid elements included in each of the first element group, the second element group, and the third element group is n and the extinction coefficient of each of the metal or metalloid elements included in each of the first element group, the second element group, and the third element group is k, The metal or metalloid element contained in the first element group is represented by the following formula (1): k≦0.01 (1) is an element that satisfies the following: The metal or metalloid element included in the second element group is a metal or metalloid element not included in the first element group, and is represented by the following formula (2): n+2k≧0.99 (2) is an element that satisfies the following: The metal or metalloid element included in the third element group is a metal or metalloid element not included in the first element group or the second element group, and is represented by the following formula (3): n≦0.89 (3) It is an element that satisfies A reflective mask blank comprising: [2] The metal or semimetal elements included in the first element group are Mo, Nb, Zr, Si, and Y; the metal or metalloid elements in the second element group are W, Au, Ir, V, Pt, Cr, Ta, Hf, Co, Ni, Sn, and Te; The metal or metalloid elements included in the third element group are Ru, Rh, and Pd. The reflective mask blank according to [1], [3] The metal or semimetal element included in the first element group is Mo; the metal or metalloid element included in the second element group is W; The metal or metalloid element included in the third element group is Ru. The reflective mask blank according to [1], [4] A reflective mask blank according to any one of [1] to [3], characterized in that the absorber film contains three or more elements selected from the group of elements each having a content of 5 atomic % or more. [5] A reflective mask blank according to any one of [1] to [4], further comprising a conductive film formed on the other main surface of the substrate. [6] A reflective mask blank according to any one of [1] to [5], characterized in that the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 240 degrees relative to the phase of the reflected light from the multilayer reflective film and the protective film. Effect of the Invention

[0013] According to the present invention, a reflective mask blank can be provided that has a thinner absorber film that ensures the necessary reflectance ratio and phase difference in a reflective mask that utilizes a phase shift function to increase the contrast of an optical image (projected image) of a pattern. Furthermore, as such a reflective mask blank, a reflective mask blank that has an absorber film with various required reflectance ratios and phase differences can be effectively manufactured. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1(A) is a cross-sectional view showing an example of a reflective mask blank RMB of the present invention, and FIG. 1(B) is a cross-sectional view showing an example of a reflective mask RM obtained by patterning the absorber film of the reflective mask blank RMB shown in (A). [Diagram 2] FIG. 13 is a diagram showing a simulation result of the contrast of a projected image of an absorber pattern. [Diagram 3] FIG. 13 shows the results of determining the refractive index n and extinction coefficient k from the film thickness, reflectance ratio, and phase difference of the absorber film (absorber pattern), where (A) is the result when the film thickness is 60 nm, (B) is the result when the film thickness is 50 nm, and (C) is the result when the film thickness is 40 nm. [Figure 4] FIG. 13 is a diagram showing the range of refractive index n and extinction coefficient k that give a predetermined reflectance ratio and phase difference when the thickness of the absorber film (absorber pattern) is within the range of 40 to 65 nm, where (A) shows the cases where the phase difference is 180 degrees, 200 degrees, and 220 degrees, and (B) shows the cases where the phase difference is 240 degrees and 260 degrees. [Diagram 5] FIG. 2 is a diagram showing the refractive index n and extinction coefficient k of a single metal material and a semi-metal material with respect to EUV light. [Figure 6] FIG. 2 is a flow diagram showing an example of a process for forming an absorber film of the present invention. [Figure 7] FIG. 6 is a diagram showing the refractive index n and extinction coefficient k of the material of the absorber film of Example 1 together with a part of FIG. 5. [Figure 8] FIG. 6 is a diagram showing the refractive index n and extinction coefficient k of the material of the absorber film in Examples 2 and 3 together with a part of FIG. 5. [Figure 9]FIG. 6 is a diagram showing a portion of FIG. 5 together with the refractive index n and extinction coefficient k of the material of the absorber film of Example 4. [Figure 10] FIG. 6 is a diagram showing a portion of FIG. 5 together with the refractive index n and extinction coefficient k of the material of the absorber film of Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will now be described in further detail. The reflective mask blank (EUV mask blank) of the present invention and a reflective mask (EUV mask) for EUV exposure will be described with reference to FIG. 1. FIG. 1(A) is a cross-sectional view showing an example of the reflective mask blank of the present invention. In the reflective mask blank RMB, a multilayer reflective film 102 that reflects EUV light, a protective film 103 therefor, and an absorber film 104 that absorbs a part of the incident EUV light and reflects the remainder are formed in this order on one main surface of a substrate, preferably a substrate 101 made of a low thermal expansion material with a sufficiently flat surface. On the other hand, a conductive film, specifically a conductive film 105 for electrostatically fixing the reflective mask to a mask stage of an exposure tool, is formed on the other main surface of the substrate 101 opposite to the surface on which the multilayer reflective film 102, the protective film 103, and the absorber film 104 are formed (rear surface).

[0016] FIG. 1(B) is a cross-sectional view showing an example of a reflective mask RM obtained by patterning the absorber film 104 of the reflective mask blank RMB shown in FIG. 1(A). The absorber film 104 can be patterned by forming a resist film on the absorber film 104, performing pattern drawing on the resist film using, for example, electron beam lithography, and forming a resist pattern, and etching away the absorber film 104 underneath using the resist pattern as a mask. This patterning forms a removed portion 111 of the absorber film and an absorber pattern 112, and by removing the remaining resist film, a reflective mask RM having a basic structure is obtained. The other components in FIG. 1(B) are given the same reference symbols as those in FIG. 1(A), and their explanations are omitted.

[0017] The substrate has a thermal expansion coefficient of preferably ±1.0×10 -8 / ℃, more preferably ±5.0×10 -9 / °C. Also, the main surface of the substrate on which the absorber film is formed is preferably surface-processed to have a high degree of flatness in the region in which the absorber pattern is formed, and the surface roughness is preferably, for example, 0.1 nm or less, particularly 0.06 nm or less in RMS representation.

[0018] The multilayer reflective film is a multilayer film in which layers of low refractive index material and layers of high refractive index material are alternately laminated, and for EUV light with an exposure wavelength of 13 to 14 nm, for example, a Mo / Si periodic laminate film in which molybdenum (Mo) layers and silicon (Si) layers are alternately laminated for about 40 periods (40 layers of each) is used. The film thickness of the multilayer reflective film is usually about 280 to 350 nm.

[0019] The protective film is also called a capping layer, and is provided to protect the multilayer reflective film when forming a pattern on the absorber film thereon or when correcting the pattern of the absorber film. The material of the protective film is silicon, ruthenium, or a compound in which niobium or zirconium is added to ruthenium, etc. The thickness of the protective film is usually about 2.5 to 4 nm. In a reflective mask blank (EUV mask blank) and a reflective mask for EUV exposure (EUV mask), the reflectance of the multilayer reflective film with the protective film laminated thereon to EUV light is usually 65 to 67%.

[0020] The conductive film is formed as necessary in order to electrostatically fix the reflective mask to the mask stage of the exposure device. The conductive film is made of a material containing chromium or tantalum as a main component. The thickness of the conductive film is usually about 20 to 300 nm.

[0021] Next, the optical characteristics required for the absorber film of the present invention will be described. When generating a projected image of a pattern on a semiconductor substrate using a reflective mask having an absorber pattern, it is necessary to obtain sufficient pattern transfer performance such as contrast of the projected image of the pattern and focal depth even in an area where the pattern dimensions are fine. For this purpose, it is necessary to set the film thickness of the absorber film (absorber pattern), the reflectance ratio and phase difference in the pattern part so that sufficient pattern transfer performance is obtained. The pattern transfer performance of the reflective mask may be evaluated by manufacturing and measuring the reflective mask, but can also be grasped by optical simulation.

[0022] FIG. 2 shows the simulation results of the contrast of the projected image of the pattern obtained when the film thickness of the absorber pattern is set to 60 nm when a dot array with a width of 17 nm and a pitch of 52 nm is transferred onto a semiconductor substrate. The horizontal axis represents the phase difference between the light reflected by the absorber pattern and the light reflected by the etched-out portion of the absorber film. The three curves in FIG. 2 are the cases where the reflectance ratio is set to 2%, 10%, or 20%, respectively. The reflectance ratio of 2% corresponds to the reflectance ratio of a conventional absorber pattern of a Ta-based material with a thickness of 70 nm, which does not take into account the use of the phase shift function (i.e., does not have a sufficient phase shift function). In contrast, the reflectance ratios of 10% and 20% are the cases where an absorber film (absorber pattern) that utilizes the phase shift function is assumed, and it can be seen that in both cases, the contrast becomes high when the phase difference is 180 degrees or more. The required phase difference varies depending on the type of pattern, the illumination conditions for the pattern, etc., but in many cases, not only in this setting, but also in many cases, the phase difference that can obtain a high contrast, for example, a contrast of 0.7 or more, which is preferable in lithography, is 180 degrees or more. Furthermore, in consideration of the transfer of hole arrays and fine line patterns, it is preferable that the phase difference is 260 degrees or less, particularly 240 degrees or less. Based on this result, it is understood that the optical constants (refractive index n, extinction coefficient k) of the absorber film (absorber pattern) required when the film thickness, reflectance ratio, and phase difference of the absorber film (absorber pattern) are set to predetermined values ​​can be obtained from the film thickness, reflectance ratio, and phase difference.

[0023] Fig. 3 is a diagram showing the results of determining the refractive index n and the extinction coefficient k from the film thickness, reflectance ratio, and phase difference of the absorber film (absorber pattern). Fig. 3(A) is a diagram showing the case where the film thickness is 60 nm. Curves 201a, 202a, and 203a show the refractive index n and the extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively. Meanwhile, curves 204a, 205a, 206a, 207a, and 208a show the refractive index n and the extinction coefficient k when the phase difference is 180 degrees, 200 degrees, 220 degrees, 240 degrees, and 260 degrees, respectively.

[0024] 3(B) shows the case where the film thickness is 50 nm. Curves 201b, 202b, and 203b show the refractive index n and extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively. Meanwhile, curves 204b, 205b, 206b, 207b, and 208b show the refractive index n and extinction coefficient k when the phase difference is 180 degrees, 200 degrees, 220 degrees, 240 degrees, and 260 degrees, respectively.

[0025] 3C shows the case where the film thickness is 40 nm. Curves 201c, 202c, and 203c show the refractive index n and extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively. Meanwhile, curves 204c, 205c, 206c, 207c, and 208c show the refractive index n and extinction coefficient k when the phase difference is 180 degrees, 200 degrees, 220 degrees, 240 degrees, and 260 degrees, respectively.

[0026] From these results, for example, the refractive index n and extinction coefficient k required for the material of an absorber film (absorber pattern) having a film thickness of 60 nm, a reflectance ratio of 10%, and a phase difference of 220 degrees are indicated by the intersection of curve 202a and curve 206a, and it is found that by specifying the film thickness of the absorber film, optical constants that give the desired reflectance ratio and phase difference can be obtained.

[0027] Furthermore, FIG. 4 shows the results of determining the range of the refractive index n and the extinction coefficient k that give a predetermined reflectance ratio and phase difference when the film thickness of the absorber film (absorber pattern) is changed from 40 nm to 65 nm. In FIG. 4(A), the regions 211a, 211b, and 211c show the refractive index n and the extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively, and the phase difference is 180 degrees. Moreover, the regions 212a, 212b, and 212c show the refractive index n and the extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively, and the phase difference is 200 degrees. Furthermore, the regions 213a, 213b, and 213c show the refractive index n and the extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively, and the phase difference is 220 degrees. On the other hand, in Fig. 4(B), the regions 214a, 214b, and 214c show the refractive index n and extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively, and the phase difference is 240 degrees. The regions 215a, 215b, and 215c show the refractive index n and extinction coefficient k when the reflectance ratio is 6%, 10%, and 20%, respectively, and the phase difference is 260 degrees. For example, in the simulation result of the contrast of the projected image of the pattern shown in Fig. 2, good contrast is obtained when the reflectance ratio is 20% and the phase difference is 220 degrees, so it can be seen that the refractive index n and extinction coefficient k in the region 213c in Fig. 4(A) should be used.

[0028] On the other hand, Fig. 5 is a diagram plotting the refractive index n and extinction coefficient k of a single metal element or metalloid element for EUV light with a wavelength of about 13.5 nm. Comparing Fig. 4 with Fig. 5, for example, in the region 213c in Fig. 4(A) where the reflectance ratio is 20% and the phase difference is 220 degrees, where good contrast is obtained in the simulation result of the contrast of the projected image of the pattern shown in Fig. 2, it can be seen that there is no material of a single metal element or metalloid element that has the refractive index n and extinction coefficient k in the region 213c. Similarly, it can be seen that there is no material of a single metal element or metalloid element that has the refractive index n and extinction coefficient k in the region 213c in the region 213a or region 213b where the reflectance ratio is 6% or 10% and the phase difference is 220 degrees, and in the region 214a, region 214b, or region 214c in Fig. 4(B) where the reflectance ratio is 6%, 10%, or 20% and the phase difference is 240 degrees. Even when the phase difference is 260 degrees, Ru may be used as a material for the protective film of the multilayer reflective film, and therefore, except for Ru which is difficult to use as a material for the absorber film, it can be seen that, for materials of single metal elements or semi-metal elements, there are no materials that have the refractive index n and extinction coefficient k in regions 215a, 215b, and 215c, which have a reflectance ratio of 6%, 10%, or 20% and a phase difference of 260 degrees, among materials of single metal elements or semi-metal elements.

[0029] In the present invention, metal elements and semimetal elements are defined and classified into three groups, a first element group, a second element group, and a third element group, as materials for the absorber film (absorber pattern) according to the refractive index n and extinction coefficient k of the simple substance, as follows. In Fig. 5, three chain lines are shown, a line 220, a line 221, and a line 222, which respectively indicate a line indicating k=0.01, a line indicating a relationship expressed by n+2k=0.99, and a line indicating n=0.89. Here, comparing Fig. 5 with Fig. 4, it can be seen that the range of the refractive index n and the extinction coefficient k in which the reflectance ratio is 6 to 20% and the phase difference is 180 to 260 degrees, specifically, most of the 15 regions (regions 211a to 215c) in Figs. 4(A) and 4(B) are present within the range surrounded by the three lines 220, 221, and 222 shown in Fig. 5 (excluding on the lines). In particular, it can be seen that the ranges of refractive index n and extinction coefficient k in which the reflectance ratio is 6 to 20% and the phase difference is 220 to 240 degrees, which are suitable for a reflective mask utilizing a phase shift function, specifically, regions 213a, 213b, 213c, 214a, 214b and 214c in Figures 4(A) and 4(B), all exist within the range surrounded by the three straight lines 220, 221 and 222 shown in Figure 5 (excluding on the straight lines).

[0030] In the present invention, the refractive index n and extinction coefficient k of a metal element or a metalloid element are as follows: (i) The following formula (1) k≦0.01 (1) A metal element or a metalloid element included in a first region in the range represented by the following formula (1) is referred to as a first element (an element included in a first element group satisfying the above formula (1)), (ii) A range not included in the first region, which satisfies the following formula (2): n+2k≧0.99 (2) A metal element or a metalloid element included in a second region in the range represented by the formula (2) is defined as a second element (an element that is not included in the first element group and is included in the second element group satisfying the formula (2) above), (iii) A range not included in either the first region or the second region, and having the following formula (3): n≦0.89 (3) A metal element or a metalloid element included in a third region in the range represented by the formula (3) is defined as a third element (an element included in the third element group that is not included in either the first element group or the second element group and satisfies the formula (3) above). Let us assume that.

[0031] Then, three or more elements, preferably three elements, are selected from two or three regions, preferably three regions, selected from the first region, the second region, and the third region, and the absorber film is composed of a material containing three or more elements, preferably three elements, selected from two or three element groups, preferably three element groups, selected from the first element group, the second element group, and the third element group. Specific examples of the material containing three or more elements, preferably three elements, include alloys consisting of only metals and semimetals, or compounds of metals or semimetals and light elements selected from nitrogen, oxygen, carbon, hydrogen, etc. In contrast, even if two or more elements are selected from only one region (one element group), it is not possible to obtain a material having a refractive index n and an extinction coefficient k such that the reflectance ratio is 6 to 20% and the phase difference is 220 to 240 degrees.

[0032] Examples of metal or semi-metal elements included in the first element group include Mo, Nb, Zr, Si, Y, Be, Ba, Ce, La, K, Ca, etc., with Mo, Nb, Zr, Si, and Y being preferred, and Mo being more preferred. Examples of metal or semi-metal elements included in the second element group include W, Au, Ir, V, Pt, Cr, Ta, Hf, Co, Ni, Sn, Te, Fe, Cu, Bi, Ag, In, Zn, Sb, Re, Os, Pb, and Mn, with W, Au, Ir, V, Pt, Cr, Ta, Hf, Co, Ni, Sn, and Te being preferred, and W being more preferred. Examples of metal or semi-metal elements included in the third element group include Ru, Rh, Pd, etc., with Ru being preferred.

[0033] The absorber film may be composed of a single layer or multiple layers. The thickness of the absorber film is preferably thin. If the absorber film is thick, it is not only disadvantageous to pattern formation, but also the pattern resolution decreases due to the shadowing effect during exposure. Therefore, the film thickness is preferably 65 nm or less, particularly 60 nm or less. On the other hand, the lower limit of the film thickness may be 20 nm or more, but is preferably 30 nm or more. Depending on the required reflectance ratio and phase difference, the film thickness may be preferably 50 nm or less, or may be preferably 40 nm or more.

[0034] The absorber film has a reflectance R of EUV light at a given film thickness. A (%) of the EUV light reflectance R of the multilayer reflective coating and protective coating B Ratio to (%) (R A / R B The content of the element selected from each element group in the absorber film can be determined so that the absorber film shifts the phase of the reflected light with respect to the phase of the reflected light from the multilayer reflective film and the protective film by a phase difference of preferably 180 degrees or more, more preferably 190 degrees or more, even more preferably 200 degrees or more, particularly preferably 210 degrees or more, particularly preferably 220 degrees or more, preferably 260 degrees or less, more preferably 240 degrees or less, within the range of preferably 0.05 or more (reflectance ratio of 5% or more), more preferably 0.06 or more (reflectance ratio of 6% or more), even more preferably 0.08 or more (reflectance ratio of 8% or more), and preferably 0.25 or less (reflectance ratio of 25% or less), more preferably 0.2 or less (reflectance ratio of 20% or less), even more preferably 0.15 or less (reflectance ratio of 15% or less). The absorber film can be formed from a material containing an element selected from each element group at a predetermined content. The content of each element selected from each element group in the absorber film is preferably 5 atomic % or more.

[0035] Specifically, in FIG. 5, the content of the element selected from each element group can be determined so that the absorber film (absorber pattern) has a desired refractive index n and extinction coefficient k within a triangle formed by connecting the plots of the elements selected from each element group with straight lines, within a range of refractive index n and extinction coefficient k such that the reflectance ratio is preferably 5% or more, more preferably 6% or more, even more preferably 8% or more, and preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less, and the phase difference is preferably 180 degrees or more, more preferably 190 degrees or more, even more preferably 200 degrees or more, particularly preferably 210 degrees or more, especially preferably 220 degrees or more, and preferably 260 degrees or less, and more preferably 240 degrees or less, for example, within the range of region 213a, region 213b, region 213c, region 214a, region 214b, or region 214c in FIG. 4(A) and FIG. 4(B).

[0036] The material having the refractive index n and the extinction coefficient k that make the reflectance ratio and the phase difference in the above range is k>0.01, n+2k<0.99, and n>0.89 It is preferable that the element is present in a range that satisfies all of the above, for example, in any of the 15 regions (regions 211a to 215c) in FIG. 4(A) and FIG. 4(B), particularly in the region 213a, region 213b, region 213c, region 214a, region 214b, and region 214c in FIG. 4(A). However, the required refractive index n and extinction coefficient k also depend on the shape and density of the pattern to be transferred and the illumination conditions for the pattern, so that the selected element and its content can be determined by taking these into consideration. In addition, this content can also be determined by simulation. Considering the 15 regions (regions 211a to 215c) shown in FIG. 4(A) and FIG. 4(B), the refractive index n is preferably 0.95 or less, more preferably 0.94 or less, and even more preferably 0.93 or less.

[0037] FIG. 6 is a flow diagram showing an example of a process for forming an absorber film of a reflective mask blank of the present invention. First, the reflectance ratio and phase difference required for the absorber film (absorber pattern) to be formed are determined by optical simulation or the like (step S301). Next, the optical constants (refractive index n and extinction coefficient k) of the absorber film (absorber pattern) are calculated in consideration of the film thickness (step S302). Next, three or more, preferably three elements are selected from two or three regions (element groups) selected from the first region (first element group), the second region (second element group), and the third region (third element group) by the above-mentioned method (step S303). Next, the content of the selected element is calculated so that the desired optical constant is obtained (step S304). This content can be calculated from the optical constant of the selected element alone and the information on the optical constant obtained in step S302. Then, the absorber film is formed so that the selected element is contained at the calculated content (step S305).

[0038] The method for forming the absorber film is preferably a sputtering method using a target containing a selected element and a sputtering gas, and magnetron sputtering is suitable for sputtering. Specifically, rare gases such as Ar gas and Kr gas can be used as the sputtering gas. In addition to the rare gas, reactive gases such as nitrogen gas (N2), oxygen gas (O2), nitrogen oxide gas (N2O, NO, NO2), carbon oxide gas (CO, CO2), and hydrocarbon gas (CH4, etc.) can be used to form the film by reactive sputtering, in which the target is sputtered. The pressure in the sputtering chamber (sputtering pressure) is preferably 0.1 Pa or more and less than 1 Pa, particularly 0.5 Pa or less.

[0039] In the manufacture of a reflective mask blank, a multilayer reflective film and its protective film are also formed prior to the formation of the absorber film, and these films can be formed by known methods. In the manufacture of a reflective mask blank, a conductive film can be formed, and the formation of the conductive film can also be carried out by known methods. The conductive film may be formed on the substrate first, or may be formed after or during the formation of the multilayer reflective film, protective film, and absorber film. EXAMPLES

[0040] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0041] [Example 1] In this example, a reflective mask having an absorber pattern with a thickness of 50 nm that gives a reflectance ratio of 10% and a phase difference of 220 degrees was considered. The refractive index n and extinction coefficient k of the material of the absorber film for forming this absorber pattern were calculated by optical simulation to be n = 0.914 and k = 0.024. Figure 7 shows the refractive index n and extinction coefficient k of the material of this absorber film together with a part of Figure 5, and the positions of the refractive index n and extinction coefficient k are indicated by point 230.

[0042] Next, molybdenum (Mo) was selected from the first region (first element group), chromium (Cr), tungsten (W), and vanadium (V) were selected from the second region (second element group), and ruthenium (Ru) was selected from the third region (third element group). In each case, the point 230 where n=0.914 and k=0.024 was included inside the triangle formed by connecting the plots of the elements selected from each element group with straight lines, and the contents of the first element, second element, and third element that result in this refractive index n and extinction coefficient k were determined.

[0043] In the case of a MoCrRu film in which molybdenum (Mo) is selected as the first element, chromium (Cr) as the second element, and ruthenium (Ru) as the third element, the content ratios of these elements are Mo=20 atomic %, Cr=46 atomic %, and Ru=34 atomic % to obtain a desired refractive index n and extinction coefficient k. In the case of a MoWRu film in which molybdenum (Mo) is selected as the first element, tungsten (W) as the second element, and ruthenium (Ru) as the third element, the content ratios of these elements are Mo=12 atomic %, W=48 atomic %, and Ru=40 atomic % to obtain a desired refractive index n and extinction coefficient k. In the case of a CrVRu film in which chromium (Cr) and vanadium (V) are selected as the second element, and ruthenium (Ru) as the third element, the content ratios of these elements are Cr=20 atomic %, V=34 atomic %, and Ru=46 atomic % to obtain a desired refractive index n and extinction coefficient k.

[0044] Next, a reflective mask blank was manufactured using the material of the absorber film. First, a multilayer reflective film that reflects EUV light and its protective film were formed in this order on one main surface of a substrate made of a low thermal expansion material. The multilayer reflective film was formed by setting the periodic length to 7.02 nm, and forming a Mo / Si multilayer reflective film (40 pairs) with a set thickness of 4.21 nm for the Si layer and 2.81 nm for the Mo layer. The protective film was formed by forming a Ru film with a thickness of 3.5 nm. The reflectance of the multilayer reflective film with this protective film formed thereon to EUV light was about 66%.

[0045] Next, an absorber film was formed on the protective film to a thickness of 50 nm. Here, from among the above three types of absorber films, a MoCrRu film with Mo=20 atomic %, Cr=46 atomic %, and Ru=34 atomic % was formed by DC magnetron sputtering using three types of targets, molybdenum, chromium, and ruthenium, and Ar gas as the sputtering gas. Furthermore, a conductive film was formed on the other main surface of the substrate to obtain a reflective mask blank.

[0046] The reflectance of the absorber film of the obtained reflective mask blank to EUV light was measured and found to be about 6.6%, and the reflectance ratio (RA / R B ) was confirmed to be 0.1 (10%) as specified. In addition, it was confirmed that the phase difference between the multilayer reflective film with protective film and the absorber film for EUV light was 220 degrees as specified.

[0047] [Example 2] In this example, the dimensions of the pattern transferred by the reflective mask are minute, but the pitch is assumed to be a coarse pattern that is about three times the pattern dimensions, and a reflective mask having an absorber pattern with a thickness of 50 nm that gives a reflectance ratio of 20% and a phase difference of 240 degrees was considered. The refractive index n and extinction coefficient k of the material of the absorber film for forming this absorber pattern were calculated by optical simulation to be n = 0.907 and k = 0.016. Figure 8 shows the refractive index n and extinction coefficient k of the material of this absorber film together with a part of Figure 5, and the positions of the refractive index n and extinction coefficient k are indicated by point 231.

[0048] Next, molybdenum (Mo) was selected from the first region (first element group), tungsten (W) was selected from the second region (second element group), and ruthenium (Ru) and palladium (Pd) were selected from the third region (third element group). In either case, the point 231 with n=0.907 and k=0.016 was included inside the triangle formed by connecting the plots of the elements selected from each element group with straight lines, and the contents of the first element, second element, and third element that result in this refractive index n and extinction coefficient k were determined.

[0049] In the case of a MoWRu film in which molybdenum (Mo) is selected as the first element, tungsten (W) as the second element, and ruthenium (Ru) as the third element, it was found that a desired refractive index n and extinction coefficient k can be obtained by setting the contents of Mo=34 atomic %, W=15 atomic %, and Ru=51 atomic %. In the case of a MoRuPd film in which molybdenum (Mo) is selected as the first element, and ruthenium (Ru) and palladium (Pd) as the third element, it was found that a desired refractive index n and extinction coefficient k can be obtained by setting the contents of Mo=59 atomic %, Ru=23 atomic %, and Pd=18 atomic %.

[0050] Next, a reflective mask blank was manufactured using the material of the absorber film. First, a multilayer reflective film that reflects EUV light and its protective film were formed in this order on one main surface of a substrate made of a low thermal expansion material. The multilayer reflective film was formed by setting the periodic length to 7.02 nm, and forming a Mo / Si multilayer reflective film (40 pairs) with a set thickness of 4.21 nm for the Si layer and 2.81 nm for the Mo layer. The protective film was formed by forming a Ru film with a thickness of 3.5 nm. The reflectance of the multilayer reflective film with this protective film formed thereon to EUV light was about 66%.

[0051] Next, an absorber film was formed on the protective film to a thickness of 40 nm. Here, from among the above two types of absorber films, a MoWRu film with Mo=34 atomic %, W=15 atomic %, and Ru=51 atomic % was formed by DC magnetron sputtering using three types of targets, molybdenum, tungsten, and ruthenium, and Ar gas as the sputtering gas. Furthermore, a conductive film was formed on the other main surface of the substrate to obtain a reflective mask blank.

[0052] The reflectance of the absorber film of the obtained reflective mask blank to EUV light was measured and found to be about 13.3%, and the reflectance ratio (R A / R B ) was confirmed to be 0.2 (20%) as specified. In addition, the phase difference between the multilayer reflective film with protective film and the absorber film for EUV light was also confirmed to be 240 degrees as specified.

[0053] [Example 3] In this example, the dimensions of the pattern transferred by the reflective mask are minute, but the pitch is assumed to be a coarse pattern that is about three times the pattern dimensions, and a reflective mask having an absorber pattern with a thickness of 40 nm that gives a reflectance ratio of 20% and a phase difference of 240 degrees was considered. The refractive index n and extinction coefficient k of the material of the absorber film for forming this absorber pattern were calculated by optical simulation to be n = 0.893 and k = 0.021. Figure 8 shows the refractive index n and extinction coefficient k of the material of this absorber film together with a part of Figure 5, and the positions of the refractive index n and extinction coefficient k are indicated by point 232.

[0054] Next, molybdenum (Mo) was selected from the first region (first element group), gold (Au) was selected from the second region (second element group), and ruthenium (Ru) and palladium (Pd) were selected from the third region (third element group). In either case, the point 232 with n=0.893 and k=0.021 was included inside the triangle formed by connecting the plots of the elements selected from each element group with straight lines, and the contents of the first element, second element, and third element that result in this refractive index n and extinction coefficient k were determined.

[0055] In the case of a MoAuRu film in which molybdenum (Mo) is selected as the first element, gold (Au) as the second element, and ruthenium (Ru) as the third element, it was found that a desired refractive index n and extinction coefficient k can be obtained by setting the contents of Mo=13 atomic %, Au=12 atomic %, and Ru=75 atomic %. In the case of a MoRuPd film in which molybdenum (Mo) is selected as the first element, and ruthenium (Ru) and palladium (Pd) as the third element, it was found that a desired refractive index n and extinction coefficient k can be obtained by setting the contents of Mo=23 atomic %, Ru=56 atomic %, and Pd=21 atomic %.

[0056] Next, a reflective mask blank was manufactured using the material of the absorber film. First, a multilayer reflective film that reflects EUV light and its protective film were formed in this order on one main surface of a substrate made of a low thermal expansion material. The multilayer reflective film was formed by setting the periodic length to 7.02 nm, and forming a Mo / Si multilayer reflective film (40 pairs) with a set thickness of 4.21 nm for the Si layer and 2.81 nm for the Mo layer. The protective film was formed by forming a Ru film with a thickness of 3.5 nm. The reflectance of the multilayer reflective film with this protective film formed thereon to EUV light was about 66%.

[0057] Next, an absorber film was formed on the protective film to a thickness of 40 nm. Here, from among the above two types of absorber films, a MoAuRu film with Mo=13 atomic %, Au=12 atomic %, and Ru=75 atomic % was formed by DC magnetron sputtering using three types of targets, molybdenum, gold, and ruthenium, and Ar gas as the sputtering gas. Furthermore, a conductive film was formed on the other main surface of the substrate to obtain a reflective mask blank.

[0058] The reflectance of the absorber film of the obtained reflective mask blank to EUV light was measured and found to be about 13.3%, and the reflectance ratio (R A / R B ) was confirmed to be 0.2 (20%) as specified. In addition, the phase difference between the multilayer reflective film with protective film and the absorber film for EUV light was also confirmed to be 240 degrees as specified.

[0059] [Example 4] In this example, assuming the transfer of a fine and dense line pattern using a reflective mask, a reflective mask having an absorber pattern with a thickness of 50 nm that gives a reflectance ratio of 20% and a phase difference of 260 degrees was considered. The refractive index n and extinction coefficient k of the material of the absorber film for forming this absorber pattern were calculated by optical simulation to be n = 0.901 and k = 0.015. Figure 9 shows the refractive index n and extinction coefficient k of the material of this absorber film together with a part of Figure 5, and the positions of the refractive index n and extinction coefficient k are indicated by point 233.

[0060] Next, molybdenum (Mo) was selected from the first region (first element group), tungsten (W) was selected from the second region (second element group), and ruthenium (Ru) was selected from the third region (third element group). The point 233 with n=0.901 and k=0.015 was included inside the triangle formed by connecting the plots of the elements selected from each element group with straight lines, and the contents of the first element, second element, and third element that result in this refractive index n and extinction coefficient k were determined.

[0061] In the case of a MoWRu film in which molybdenum (Mo) is selected as the first element, tungsten (W) as the second element, and ruthenium (Ru) as the third element, it was found that a specified refractive index n and extinction coefficient k could be obtained by setting the contents of Mo = 29 atomic %, W = 6 atomic %, and Ru = 65 atomic %.

[0062] Next, a reflective mask blank was manufactured using the material of the absorber film. First, a multilayer reflective film that reflects EUV light and its protective film were formed in this order on one main surface of a substrate made of a low thermal expansion material. The multilayer reflective film was formed by setting the periodic length to 7.02 nm, and forming a Mo / Si multilayer reflective film (40 pairs) with a set thickness of 4.21 nm for the Si layer and 2.81 nm for the Mo layer. The protective film was formed by forming a Ru film with a thickness of 3.5 nm. The reflectance of the multilayer reflective film with this protective film formed thereon to EUV light was about 66%.

[0063] Next, an absorber film was formed on the protective film to a thickness of 50 nm. Here, a MoWRu film with Mo=29 atomic %, W=6 atomic %, and Ru=65 atomic % was formed as the absorber film by DC magnetron sputtering using three types of targets, molybdenum, tungsten, and ruthenium, and Ar gas as the sputtering gas. Furthermore, a conductive film was formed on the other main surface of the substrate to obtain a reflective mask blank.

[0064] The reflectance of the absorber film of the obtained reflective mask blank to EUV light was measured and found to be about 13.4%, and the reflectance ratio (R A / R B) was confirmed to be 0.2 (20%) as specified. In addition, it was confirmed that the phase difference between the multilayer reflective film with protective film and the absorber film for EUV light was 260 degrees as specified.

[0065] [Example 5] In this example, a reflective mask having an absorber pattern with a thickness of 50 nm that gives a reflectance ratio of 20% and a phase difference of 180 degrees was considered, which has a high transferred image intensity level and is advantageous in terms of exposure throughput, although the contrast during pattern transfer is somewhat inferior. The refractive index n and extinction coefficient k of the material of the absorber film for forming this absorber pattern were calculated by optical simulation to be n = 0.931 and k = 0.018. Figure 10 shows the refractive index n and extinction coefficient k of the material of this absorber film together with a part of Figure 5, and the positions of the refractive index n and extinction coefficient k are indicated by point 234.

[0066] Next, molybdenum (Mo) was selected from the first region (first element group), and tungsten (W) and vanadium (V) were selected from the second region (second element group), for a total of three elements. No elements were selected from the third region (third element group). Point 234 with n=0.931 and k=0.018 was included inside the triangle formed by connecting the plots of the elements selected from each element group with straight lines, and the contents of the first and second elements that result in this refractive index n and extinction coefficient k were determined.

[0067] In the case of a MoWV film in which molybdenum (Mo) is selected as the first element and tungsten (W) and vanadium (V) are selected as the second elements, it was found that a specified refractive index n and extinction coefficient k could be obtained by setting the contents of Mo = 46 atomic %, W = 25 atomic %, and V = 29 atomic %.

[0068] Next, a reflective mask blank was manufactured using the material of the absorber film. First, a multilayer reflective film that reflects EUV light and its protective film were formed in this order on one main surface of a substrate made of a low thermal expansion material. The multilayer reflective film was formed by setting the periodic length to 7.02 nm, and forming a Mo / Si multilayer reflective film (40 pairs) with a set thickness of 4.21 nm for the Si layer and 2.81 nm for the Mo layer. The protective film was formed by forming a Ru film with a thickness of 3.5 nm. The reflectance of the multilayer reflective film with this protective film formed thereon to EUV light was about 66%.

[0069] Next, an absorber film was formed on the protective film to a thickness of 50 nm. Here, a MoWV film with Mo=46 atomic %, W=25 atomic %, and V=29 atomic % was formed as the absorber film by DC magnetron sputtering using three types of targets, molybdenum, tungsten, and vanadium, and Ar gas as the sputtering gas. Furthermore, a conductive film was formed on the other main surface of the substrate to obtain a reflective mask blank.

[0070] The reflectance of the absorber film of the obtained reflective mask blank to EUV light was measured and found to be about 13.4%, and the reflectance ratio (R A / R B ) was confirmed to be 0.2 (20%) as specified. In addition, it was confirmed that the phase difference between the multilayer reflective film with protective film and the absorber film for EUV light was 180 degrees as specified. [Explanation of symbols]

[0071] 101 Substrate 102 Multilayer reflective film 103 Protective film 104 Absorber membrane 105 Conductive film 111 Absorber film removal section 112 Absorbent Pattern RMB Reflective Mask Blank RM Reflective Mask

Claims

1. A reflective mask blank comprising a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of incident EUV light and reflects the remainder, formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film for EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25; the absorber film has a function of shifting the phase of the reflected light by a phase difference of 200 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, the absorber film is made of a material containing, as metal elements or semimetal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group, and one or more elements selected from each of the two or three element groups; When the refractive index of each of the metal or metalloid elements contained in each of the first element group, the second element group, and the third element group is n and the extinction coefficient of each of the metal or metalloid elements alone is k, The metal or metalloid element contained in the first element group is represented by the following formula (1): k≦0.01 (1) is an element that satisfies the following: The metal or metalloid element included in the second element group is a metal or metalloid element not included in the first element group, and is represented by the following formula (2): n+2k≧0.99 (2) is an element that satisfies the following: The metal or metalloid element included in the third element group is a metal or metalloid element not included in the first element group or the second element group, and is represented by the following formula (3): n≦0.89 (3) It is an element that satisfies A reflective mask blank comprising:

2. The metal or semi-metal elements included in the first element group are Mo, Nb, Zr, Si, and Y; The metal or metalloid elements included in the second element group are W, Au, Ir, V, Pt, Cr, Ta, Hf, Co, Ni, Sn, and Te; The metal or metalloid elements included in the third element group are Ru, Rh, and Pd.

2. The reflective mask blank according to claim 1 .

3. 3. The reflective mask blank according to claim 1, wherein the absorber film contains three or more elements selected from the group of elements each having a content of 5 atomic % or more.

4. The reflective mask blank according to any one of claims 1 to 3, characterized in that the absorber film has a function of shifting the phase of reflected light by a phase difference of 200 to 240 degrees relative to the phase of reflected light from the multilayer reflective film and the protective film.

5. A reflective mask blank comprising a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of incident EUV light and reflects the remainder, formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film for EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25; the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, the absorber film is made of a material containing, as metal elements or semimetal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group, and one or more elements selected from each of the two or three element groups; The metal or semi-metal elements included in the first element group are Mo, Nb, Zr, Si, and Y; the metal or metalloid elements in the second element group are W, Au, Ir, V, Pt, Cr, Hf, Co, Sn, and Te; The metal or metalloid elements included in the third element group are Ru, Rh, and Pd. A reflective mask blank comprising:

6. 6. The reflective mask blank according to claim 5, wherein the absorber film contains three or more elements selected from the group of elements each having a content of 5 atomic % or more.

7. A reflective mask blank comprising a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of incident EUV light and reflects the remainder, formed in this order on one main surface of a substrate, The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film for EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25; the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, the absorber film is made of a material containing, as metal elements or semimetal elements, three or more elements selected from two or three element groups selected from a first element group, a second element group, and a third element group, and one or more elements selected from each of the two or three element groups; When the refractive index of each of the metal or metalloid elements contained in each of the first element group, the second element group, and the third element group is n and the extinction coefficient of each of the metal or metalloid elements alone is k, The metal or metalloid element contained in the first element group is represented by the following formula (1): k≦0.01 (1) is an element that satisfies the following: The metal or metalloid element included in the second element group is a metal or metalloid element not included in the first element group, and is represented by the following formula (2): n+2k≧0.99 (2) is an element that satisfies the following: The metal or metalloid element included in the third element group is a metal or metalloid element not included in the first element group or the second element group, and is represented by the following formula (3): n≦0.89 (3) is an element that satisfies the following: The content of each of the three or more elements selected from the group of elements in the absorber film is 5 atomic % or more. A reflective mask blank comprising:

8. The metal or semi-metal elements included in the first element group are Mo, Nb, Zr, Si, and Y; The metal or metalloid elements included in the second element group are W, Au, Ir, V, Pt, Cr, Ta, Hf, Co, Ni, Sn, and Te; The metal or metalloid elements included in the third element group are Ru, Rh, and Pd. The reflective mask blank according to claim 7 .

9. The reflective mask blank according to any one of claims 5 to 8, characterized in that the absorber film has a function of shifting the phase of reflected light by a phase difference of 180 to 240 degrees relative to the phase of reflected light from the multilayer reflective film and the protective film.

10. The metal or semi-metal element included in the first element group is Mo; The metal or metalloid element included in the second element group is W, The metal or metalloid element included in the third element group is Ru. The reflective mask blank according to any one of claims 1 to 9.

11. 11. The reflective mask blank according to claim 1, further comprising a conductive film formed on the other main surface of the substrate.

12. A reflective mask blank described in any one of claims 1 to 11, characterized in that the thickness of the absorber film is 30 nm or more and 65 nm or less.

13. a reflective mask blank comprising a multilayer reflective film that reflects EUV light, a protective film, and an absorber film that absorbs a portion of incident EUV light and reflects the remainder, formed in this order on one main surface of a substrate; The reflectance R of the absorber film for EUV light A (%), the reflectance R of the multilayer reflective film and the protective film for EUV light B Ratio to (%) (R A / R B ) is 0.05 to 0.25; the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 260 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film, A method for producing a reflective mask blank, wherein the absorber film contains a metal element or a metalloid element, When the refractive index of the metal element or metalloid element alone is n and the extinction coefficient of the metal element or metalloid element alone is k, The refractive index n and the extinction coefficient k are expressed by the following formula (1): k≦0.01 (1) A first element included in a first region in the range indicated by The refractive index n and the extinction coefficient k are not included in the first region and are expressed by the following formula (2): n+2k≧0.99 (2) A second element included in a second region in the range indicated by A range not included in the first region or the second region, and a range represented by the following formula (3) n≦0.89 (3) A third element included in a third region in the range indicated by A step of classifying selecting, from two or three regions selected from the first region, the second region, and the third region, three or more elements, the one or more elements being selected from each of the two or three regions; The absorber film has a predetermined thickness and the ratio (R A / R B determining the content of each of the three or more elements selected from the region so as to obtain a predetermined ratio within the range of the phase difference and a predetermined phase difference within the range of the phase difference; forming an absorber film from a material containing each of the three or more elements selected from the region at the determined content ratio; A method for producing a reflective mask blank, comprising:

14. 14. The method according to claim 13, further comprising the step of forming a conductive film on the other main surface of the substrate.

15. 15. The method according to claim 13, wherein the absorber film has a function of shifting the phase of the reflected light by a phase difference of 180 to 240 degrees with respect to the phase of the reflected light from the multilayer reflective film and the protective film.

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